Barium (Ba) is an element which is toxic to humans, plants, and animals. Deciphering the geochemical behavior of Ba in soils is fundamental for assessing the potentials risks posed by Ba. Ba isotopes are a potentially robust tracer of Ba in soils. In this study, the controlling factors of Ba isotopic fractionation in a latosol profile were investigated through sequential-extraction experiments. Furthermore, dissolution experiments were conducted to understand Ba isotopic fractionation during the dissolution of basalts. The sequential-extraction experiments revealed δ^137/134Ba ratios in various fractions that were remarkably heterogeneous: −0.28‰ to −0.15‰ in the exchangeable fraction; −0.32‰ to −0.16‰ in reducible Fe-Mn (oxyhydr)oxides; and 0.06‰ to 0.46‰ in residues. This indicates that light Ba isotopes are preferentially adsorbed on secondary minerals and associated with Fe-Mn (oxyhydr)oxides. Both processes play important roles in storing Ba originally released from minerals. Results of the sequential-extraction and dissolution experiments revealed that light Ba isotopes favored fluids during the dissolution of silicate minerals, while heavy Ba isotopes were prone to being released from interlayers of micaceous layers. Collectively, the dissolution of minerals, adsorption on secondary minerals, and formation of easily reducible Fe-Mn (oxyhydr)oxides govern Ba isotope fractionation and Ba transport in soils.

钡（Ba）是对人类，植物和动物有毒的元素。评估土壤中Ba的地球化学行为对于评估Ba构成的潜在风险至关重要。钡同位素是土壤中钡的潜在强效示踪剂。在这项研究中，通过顺序提取实验研究了Latosol剖面中Ba同位素分馏的控制因素。此外，进行了溶出实验以了解玄武岩溶出过程中的Ba同位素分馏。顺序萃取实验显示^{δ13​​7/134}不同比例的馏分中的Ba比率非常不均：可交换馏分中的-0.28‰至-0.15‰；可还原的Fe-Mn（羟基）氧化物的-0.32‰至-0.16‰; 残留量为0.06‰至0.46‰。这表明轻钡同位素优先吸附在次生矿物上，并与Fe-Mn（羟基）氧化物有关。这两种过程在储存最初从矿物中释放出来的Ba方面都起着重要作用。顺序萃取和溶解实验的结果表明，轻质钡同位素在硅酸盐矿物溶解过程中有利于流体，而重质钡同位素则易于从云母层的夹层中释放出来。总的来说，矿物的溶解，次生矿物的吸附以及易还原的Fe-Mn（羟基）氧化物的形成决定着Ba同位素的分馏和土壤中Ba的迁移。